My PCSX2 slows down these days.I didn't change anything to my computer.But the emulator itself did!Even if I changed to a older version of PCSX2,It came the same result.

The same game I runned 60fps before.Now only 40~50fps(in some scene).

It happened when I set the graph menu to "DirectX9 Hardware T&L" mode.After I enter the game,the speed went down.Then I pressed "esc" to the menu, choose "DirectX9 software T&L"mode,then back to the game,the speed returns to 60FPS full speed!!!(in 2D scene)
And if I just selected "DirectX9 software T&L"mode before entering the game,the PCSX2 crashed.

Besides,I didn't turn on any Speed Hacks and patches.
My video card is ATI HD5830.I didn't overload my CPU.My PC runs other PC games well such as Fallout3,Call of duty BO.
I don't think it connect to my hardware because I run the PCSX2 full speed just before and I didn't change anything.

One more thing,the 0.97 ver and olders can't run the "Zill oll"(A japanese RPG by KOEI).The game can't save,and into some scene the PCSX2 goes to blackscreen.

keep your eyes on the temps,and how it goes while pcsx2 is running?
I think its a stability issue, as long as you didn't change anything, there is either a bug with the emulator(which I doubt) or there is something going wrong inside your machine.